Mary replacement chainring, chain and cog?

My 2009 Mary chainring is showing signs of wear...on the acceleration side of course. The stocker is aluminum and I've re-tensioned the chain several times. Is a chain checker the best way to know when it's worn out? If so, what is a good one? On my geared bike I can tell by the way the cassette gets sharp edges sticking out from the sides of the most used cogs (as the teeth get worn and smashed out to the sides if that makes sense.)

Aluminum is lightweight, but steel should last longer and not that much more weight. IIRC titanium is nice compromise of weight and wear, not sure on the wear part though and maybe kinda spendy. Stock chain is KMC, but not sure what part number. Rear cog is just cheapie stamped steel.

What is a good replacement chainring, chain, and rear cog that will last? What are you all using?

A ruler is the best way to check a chain IMO. 12 links should equal 12 inches. Its a pretty good idea to replace it once it is 1/16" stretched and definitely a requirement once it reaches 1/8" stretched.

A word of advice: if you check your chain regularly and replace it when you notice it is stretched out you shouldn't necessarily have to replace either the chainring or the cog. A stretched chain eats through the ring and cog much quicker than just regular wear and tear. You should be able to get multiple chains worth of life out of the same drivetrain

KMC chains are pretty good and I have gotten good life out of those stamped cogs too, so I don't see any reason not to replace with the same. Both can be found cheap online

On my geared bikes, the rollers at each link wore out before the chain actually had any noticeable stretch measured as you said....but a chain checker that goes in between the links showed the wear....I thought it was kinda odd. This is my first SS though so I'm still learning. Rotated my chainring 90 degrees forward last night when I was cleaning and lubing to move the wear more evenly around the chainring.